1. Field of the Disclosure
The present invention relates to a method for fabricating a semiconductor device, and more particularly, to a method for fabricating a photomask.
2. Brief Description of Related Technology
In a process of fabricating a semiconductor device, a photomask onto which a pattern is formed is used for patterning the semiconductor substrate. The pattern of the photomask is transferred onto a wafer by a photolithography process. Accordingly, the manufacturing process of the photomask is considered to be very significant. As semiconductor devices become more highly integrated, the patterns on the photomask are formed with a smaller critical dimension (CD). In the fabrication of the photomask, margin reduction in the etching process and foreign materials on a resist layer may create patterns having CDs different from the CD of a target pattern.
For the CD accuracy of a pattern on a photomask, a CD correction process to correct the CD of a photomask pattern is performed after the fabrication of the photomask. After all the processes in the fabrication of a photomask have been completed, the first step in the correction process is to measure the CD of a mask pattern on the photomask. The CD of the mask pattern is compared with that of a target pattern to check whether the CD of the mask pattern corresponds to that of the target pattern. The CD of the mask pattern is corrected by additionally etching the mask pattern by a difference between the CD of the mask pattern and the CD of a target pattern.
The additional etching of the mask pattern is performed using a separate correction mask after all the processes in the fabrication of a photomask have been completed. The separate correction mask may increase processing time and fabrication cost because it involves an additional resist coating process and exposure and development process. Furthermore, foreign materials left by the additional processes may degrade the quality of the photomask, and influences of the fabrication processing environments and equipment make it difficult to ensure pattern reproducibility.